Crystal structures of Staphylococcal SaeR reveal possible DNA-binding modes

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• The Staphylococcus SaeRS two-component system regulates virulence factor expression.
• SaeS, a sensor histidine kinase, phosphorylates SaeR, a DNA-binding regulator.

Purpose of the Study:

• To determine the crystal structures of the SaeR DNA-binding domain (DBD) from Staphylococcus epidermidis and Staphylococcus aureus.
• To analyze the DNA binding activity of SaeR mutants to understand its interaction with DNA.

Main Methods:

• X-ray crystallography was used to determine the 3D structures of the SaeR DBD.
• Site-directed mutagenesis was employed to create SaeR mutants for DNA binding assays.

Main Results:

• The crystal structures of SaeR DBD from S. epidermidis and S. aureus revealed similar protein folds.
• Mutational analysis indicated that Thr217 is crucial for binding to DNA's phosphate group, and Trp219 may interact with DNA base pairs.
• The tandem arrangement of the DBD suggests a potential mechanism for SaeR oligomerization on DNA.

Conclusions:

• SaeR DBD structures provide insights into the molecular basis of DNA recognition in Staphylococcus.
• Specific amino acid residues (Thr217, Trp219) play key roles in SaeR-DNA interactions.
• The findings suggest a model for SaeR binding and potential oligomerization on target DNA sequences, impacting virulence regulation.